Logical resource partitioning of a data processing system

• US 4,843,541 A
• Filed: 07/29/1987
• Issued: 06/27/1989
• Est. Priority Date: 07/29/1987
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: McCauley, Donald W., Rathjen, John C., Bean, George H., Rakhmilevich, Mark E., Wyman, Leslie W., Farrell, Mark S., Scalzi, Casper A., Johnson, Francis E., Hough, Roger E., Borden, Terry L., Scanlon, John F., Gum, Peter H.
• Primary Examiner(s): Chan, Eddie P.
• Assistant Examiner(s): Kulik, Paul
• Application Number:
  US07/079,314
• Time in Patent Office: 699 Days
• Field of Search: 364/300, 364/200, 364/900, 364/200 MS File, 364/900 MS File
• US Class Current: 710/36
• CPC Class Codes: G06F 9/4843 by program, e.g. task dispatcher, supervisor, operating system
• CPC Class Codes: G06F 9/5077 Logical partitioning of resources; Management or configuration of virtualized resources specific details on emulation or internal functioning of virtual machines G06F9/455

Abstract

The embodiment discloses a method and means for partitioning the resources in a data processing system into a plurality of logical partitions. Host control code may be embodied in programming, microcode, or by special hardware to enable highly efficient operation of a plurality of preferred guest programming systems in the different partitions of the system. The main storage, expanded storage, the channel, and subchannel resources of a system are assigned to the different logical partitions in the system to enable a plurality of preferred guest programming systems to run simultaneously in the different partitions. This invention automatically relocates the absolute addresses of the I/O channel and subchannel resources in the system to their assigned partitions. Also the absolute and virtual addresses of the different guest programming systems are relocated into, as well as page addresses for any expanded storage, their assigned partitions. The guest programming systems generally will be different operating systems. The logical CPU(s) of the guests are dispatched on one or plural real CPUs in the system using the S/370XA SIE (start interpretive execution) instruction. Special operations are provided, including the CPU alerting of other guests in different partitions using I/O interruption signalling. Interception is provided to handle special circumstances.

Claims

1. A method of restricting guest operations in a data processing system to system resources assigned to a guest, the resources in the system including one or more real CPUs, a system main storage (MS), an optional system extended storage (ES), and a plurality of I/O channels using I/O processors for connecting to the system a plurality of I/O device control units with their I/O devices, a host hypervisor (host) which includes software, the host supervising plural software control programs (guests) capable of concurrently and independently operating in the system and the guests may be the same or different types of control programs, subchannels (SCHs) for representing I/O devices to the host and to the guests, each guest being restricted to using an assigned subset (partition) of system resources, the method for restricting guest operations comprising:

providing a plurality of partition sets in system storage for defining partitions of system resources, each partition set defining a particular subset of system resources available to a guest assigned to use the partition, each partition set comprised of a plurality of entries for specifying the system resources assigned to the partition and the items being enterable by a human operator, the items assignable to each partition set including indicators for;

a unique partition identifier (AZN), a MS zone of contiguous main sotrage which can be located anywhere in MS and bounded by upper and lower limit MS addresses, none or mone or plural SCHs, and an optional ES zone located anywhere in ES and bounded by upper and lower limit ES addresses,

having a control block in system storage for each SCH, each SCH containing an identifier for an I/O interrupt queue assigned to the SCH, each SCH being capable of being assigned to none, one or plural partition sets as indicated by none, one or more AZNs being set into the control block of the SCH,

also having a plurality of state description control blocks (SDs) in system storage for representing logical CPUs in the system, each SD containing fields with parameters for defining a logical CPU,

binding a logical CPU to a particular partition by entering the AZN of a respective partition set into the SD representing the logical CPU,

assigning a logicl CPU to a particular guest by entering parameters of the guest into the SD of the logical CPU,

dispatching a logical CPU for a guest on a selected real CPU in the data processing system by the host executing a start interpretive execution (SIE) instruction on the real CPU to start execution of the logical CPU for the guest in the partition assigned by the AZN in the SD of the logical CPU,

assigning an I/O device to a guest by setting the AZN assigned to the guest'"'"'s partition set into an SCH of the I/O device and setting an identifier of the SCH into the guest'"'"'s partition set and into the SD of each logical CPU which is to use the SCH,

setting a pass-through indicator in a SCH of an I/O device assigned to a guest to enable the direct routing of I/O instructions from, and of pending I/O interruptions to the logical CPU of the guest in order to allow each guest to directly control guest assigned I/O devices without host assistance during normal execution of I/O operations by a guest'"'"'s logical CPU,

allowing a guest to directly insruct, and to directly handle I/O interruptions for, an I/O devie assigned to the guest by determining that the SCH of the I/O device is set with the same AZN as is set into the SD of the logical CPU dispatched for the guest to allow the guest to control its assigned I/O devices without host intervention, and to restrict each guest to using only the SCHs having the same AZN identified in both the SCH and the partition set assigned to the guest.

2. A method of restricting guest operations in a data processing system as defined in claim 1, further comprising:

relocating all channel addresses used by a SCH into a MS zone assigned to the partition indicated by the AZN assigned to the SCH, and

checking channel accesses to MS in relation to the boundaries of the MS zone assigned to the partition identified by the AZN assigned to the SCH, and

indicating any violation by any channel access outside of the assigned MS zone.

3. A method of restricting guest operations in a data processing system as defined in claim 1, further comprising:

providing a partition pointer table for accessing the partition definition sets in any order, and receiving assignments of AZNs for enabling any AZN value to be assigned to any partition definition table,

dispatching on a real CPU a highest priority logical CPU of the logical CPUs ready to execute.

4. A method of restricting guest operations in a data processing system as defined in claim 2, further comprising:

enabling a dispatched guest on a real CPU to detect the existence of I/O interruptions for one or more SCHs assigned to another guest which is assigned to another partition and not currently dispatched on a real CPU,

alerting the host after the dispatched guest receives an I/O interruption for a SCH assigned to the other guest, and

the host making ready for dispatch the other guest having the I/O interruption.

5. A method of restricting guest operations in a data processing system as defined in claim 4, further comprising:

comparing a dispatching priority of the currently dispatched guest with a dispatching priority of any other guest made ready for dispatch by the host to determine which guest is to be dispatched next on the real CPU of the currently dispatched guest,

terminating the dispatch of the currently dispatched guest for a dispatch of another guest having a dispatching priority higher than the current guest.

6. A method of restricting guest operations in a data processing system as defined in claim 5, further comprising:

intercepting the execution of the dispatched guest when an I/O interruption becomes pending for a SCH assigned to an alertable other guest when the dispatched guest is enabled for the I/O interruption,

invoking host processing on the CPU of the intercepted guest to detect the I/O interruption of the alertable guest and make the alertable guest ready for dispatching.

7. A method of restricting guest operations in a data processing system as defined in claim 6, processing by the host further comprising:

detecting if there are still other pending I/O interruptions for still other guest(s) enabled for alerting by the intercepted guest and having a pending I/O interruption(s),

making each of the still other detected guest(s) ready for dispatching, and

dispatching the highest-priority of the guests made ready for dispatching.

8. A method of restricting guest operations in a data processing system as defined in claim 1, further comprising:

having indicators in the SCHs of the assignment of the SCHs to hardware and guest I/O interruption queues,

providing a guest I/O interruption enablement mask (GIEM) in the SD of each partition-assigned guest for selectively indicating the guest'"'"'s I/O interruption enablement state for handling pending interruptions on guest I/O interruption queues,

providing an effective I/O interruption enablement mask (EIEM) for use by the host and any dispatched partition-assigned guest to selectively indicate the I/O interruption enablement states for the hardware I/O interruption queue(s) usable by the guest including;

at least one hardware queue for receiving the I/O interruptions of the dispatched guest and other hardware queue(s) for receiving the I/O interruption(s) of one or more other guests alertable by the dispatched guest,

processing and loading the EIEM into a host control register of a real CPU on which the guest is being dispatched,

setting on a disabling field in the SD of the guest when the guest is found selectively disabled for handling an I/O interruption by a subchannel assigned to the guest, including setting on the disabling field after the guest makes a change in its GIEM, the on state of the disabling field preventing the guest from handling any I/O interruption for any subchannel asigned to the guest.

9. A method of restricting guest operations in a data processing system as defined in claim 8, further comprising:

alerting the host whenever the dispatched guest receives an I/O interruption for a subchannel assigned to another partition enabled by the EIEM in the CPU of the dispatched guest, even though the SD disabling field of the dispatched guest is set off or the EIEM in the CPU of the dispatched guest is disabling the dispatched guest in order to prevent the dispatched guest from handling its own I/O interruptions.

10. A method of restricting guest operations in a data processing system as defined in claim 8, executing a test pending instruction (TPI) comprising:

testing the state of an SD queuing indicator field for the dispatched guest to determine if the dispatched guest has any I/O pending interruptions for any SCH'"'"'s assigned to the dispatched guest in any guest queue,

intercepting the processing of the TPI instruction if the SD queuing indicator field of the dispatched guest is on, but

invoking the host to execute a TPI instruction for the guest to determine if there is any pending I/O interruption for the guest on a hardware I/O interruption queue used for receiving guest I/O interruptions.

11. A method of restricting guest operations in a data processing system as defined in claim 10, further processing the test pending instruction (TPI) comprising:

providing a partition mode field in each SD to indicate if the respective guest is assigned to a partition-assigned guest,

providing an I/O interrupt pending register (IPR) in each CPU having IPR bit positions that respectively indicate if any I/O interruption is pending in an associated hardware I/O interrupt queue of which at least one queue is assigned for the use of each partition-assigned guest,

setting on a condition code (CC) in a program status word (PSW) of the guest to a first predetermined state when the guest'"'"'s respective IPR bit position indicates no I/O interruption is pending for the guest, and

ending the operation for the TPI instruction.

12. A method of restricting guest operations in a data processing system as defined in claim 11, further processing the test pending instruction (TPI) comprising:

dequeuing an I/O interruption if the guest is in partitioned mode and the guest'"'"'s IPR bit position indicates an I/O interruption is pending for a subchannel assigned to the guest,

testing if a pass-through field is set on in the interrupting subchannel,

intercepting the processing of the TPI instruction if the pass-through field is set off in the interrupting subchannel, and invoking processing by the host to set on the pass-through field to enable the guest to handle the I/O interruption.

13. A method of restricting guest operation in a data processing system as defined in claim 12, the processing for a test pending instruction (TPI) further comprising:

testing the GIEM of the disptched guest to determine whether the guest is selectively enabled for a pending I/O interruption when the state of the pass-through field indicates the guest may handle the I/O interruption,

storing an I/O interruption code in the SD of the dispatched guest when the testing operation finds the guest is selectively enabled,

setting on a condition code (CC) in the PSW of the guest to a second predetermined state when the storing operation has stored the I/O interruption, and

ending the operation for the TPI instruction.

14. A method of restricting guest operations in a data processing system as defined in claim 13, the processing for a test pending instruction (TPI) further comprising:

intercepting the guest processing of the TPI instruction by storing an intercept code if the testing operation finds the dispatched guest is disabled by its GIEM from handling the I/O interruption, and

invoking processing by the guest to enable the GIEM for the guest to handle the I/O interruption.

15. A method of restricting guest operations in a data processing system as defined in claim 8, executing a test subchannel (TSCH) instruction issued by a guest dispatched on a CPU to determine if the subchannel has any I/O interruption pending for the guest, comprising:

testing the state of the partition mode field in the SD of the dispatched guest to determine if the partition mode field indicates the guest is a partition-assigned guest,

testing if the I/O interrupting subchannel is partition-assigned to the dispatched guest,

and testing a pass-through field in the subchannel to determine if I/O interruptions of the subchannel can be handled by partition-assigned guests,

intercepting the processing of the TSCH instruction if any of the testing operations find the SD partition-mode field of the dispatched guest is set off, or the guest I/O interruption queue assignment in the subchannel being tested is not for the partition assigned to the dispatched guest, or if the pass-through field is set off in the subchannel being tested,

invoking the host to execute a TSCH instruction for the guest to determine if the subchannel has any pending I/O interruption for the guest.

16. A method of restricting guest operations in a data processing system as defined in claim 15, executing a test subchannel (TSCH) instruction issued by a guest dispatched on a CPU to determine if the subchannel has any I/O interruption pending for the guest, comprising:

dequeuing any I/O interruption found for the subchannel being tested when the testing operations find the SD partition-mode field of the dispatched guest is set on, and the guest I/O interruption queue assignment in the subchannel being tested is for the partition assigned to the dispatched guest, and the pass-through field is set on in the subchannel being tested,

testing if any I/O exception condition exists to the execution of the TSCH instruction and

if an exception condition is found to exist, setting off the pass-through field and setting a predetermined intercept code in the SD of the dispatched guest,

intercepting the processing of the TSCH instruction, and

invoking the host to execute a TSCH instruction for the guest.

17. A method of restricting guest operations in a data processing system as defined in claim 16, executing a test subchannel (TSCH) instruction issued by a guest dispatched on a CPU to obtain subchannel status for the guest, comprising:

obtaining and storing an information response block (IRB) containing subchannel status in guest storage if no exception condition is found by the testing operation,

providing an I/O status pending field in each subchannel to indicate if any I/O status is pending for the subchannel, and copying the state of the field into the IRB,

testing the I/O status pending field in the IRB to determine if any I/O status is pending for the subchannel,

setting on a condition code (CC) in a program status word (PSW) of the guest to a first predetermined state when the I/O status pending field indicates an I/O status is pending for the subchannel being tested,

setting on a condition code (CC) in the PSW of the guest to a second predetermined state when the I/O status pending field indicates no I/O status is pending for the subchannel being tested, and

ending the operation for the TSCH instruction.

18. A method of restricting guest operations in a data processing system as defined in claim 1, further comprising:

providing in the SD of each partition-assigned guest an alerting I/O interruption enablement mask (AZM) for selectively indicating which of plural hardware I/O interrupt queues can be monitored by the guest for alerting other guests, and a guest I/O interruption enablement mask (GIEM) for selectively indicating the enablement state for the guest'"'"'s I/O interrupt queues,

providing an effective I/O interruption enablement mask (EIEM) for use by a dispatched partition-assigned guest to selectively indicate the guest'"'"'s enablement states;

for hardware I/O interruption queue(s) on which I/O interruptions can be handled by the dispatched guest and for hardware I/O interruption queue(s) on which I/O interruption(s) for other guest(s) can cause alerting by the dispatched guest,

processing and loading the EIEM into a control register of the real CPU of the guest,

selecting a pending I/O interruption on any hardware queue that is enabled by the EIEM for examination by the dispatched guest,

testing if the I/O interruption is enabled by the AZM for another guest,

identifying the AZN in the SCH providing the I/O interruption if the testing operation finds the I/O interruption is for another guest being alerted,

storing the AZN of the alerting guest in the SD of the dispatched guest,

setting an intercept code into the SD of the dispatched guest to indicate an alerting intercept condition, and

intercepting the guest'"'"'s dispatch to invoke the host to examine the AZN of the alerting guest in the SD of the dispatched guest to make the alerting guest ready for dispatching.

19. A method of restricting guest operations in a data processing system as defined in claim 18, the host invocation for the alerting guest further comprising:

determining the AZN for any other guest enabled in the AZM in the SD of the dispatched guest,

executing a test pending zone interrupt (TPZI) instruction for each other guest'"'"'s AZN identified by the determining operation to determine if any pending I/O interruption exists for any other guest enabled by the AZM of the dispatched guest,

making ready for dispatch each other guest found by the executing operation to have a pending I/O interruption,

and dispatching the ready guest having a highest dispatching priority.

20. A method of restricting guest operations in a data processing system as defined in claim 1, executing a test pending zone interrupt (TPZI) instruction for determining if any pending I/O interruption exists for a guest identified by a specified AZN, further comprising:

finding that no exception conditions exist at the beginning of execution of the TPZI that may interfere with its execution,

providing in a first general register associated with the TPZI;

a control field to indicate whether a first or second type of response is to be provided by the TPZI, an AZN field specifying the AZN of a guest being examined for I/O interruptions, and a GIEM field containing a GIEM (guest I/O interruption enablement mask) for the guest,

providing in a second general register associated with the TPZI an address of a storage location where a response to the TPZI is to be stored,

having an I/O interrupt pending register (IPR) in each CPU with respective IPR bit positions that respectively indicate whether any I/O interruption is pending in each of respectively associated hardware I/O interrupt queues, at least one assigned IPR bit position being assigned for use by a guest regarding the guest'"'"'s use of a corresponding hardware queue that receives the guest'"'"'s I/O interruptions,

examining the state of the assigned IPR bit position for the guest to find if any pending I/O interrupt exists for the guest, and setting a condition code in a host program status word (PSW) to a first value to indcate when no pending I/O interruption exists for the guest being examined,

storing I/O information about any pending I/O interruption when the first general register indicates a first type response is to be provided, and setting the condition code in the host PSW to a first value to indicate the second type response has been provided,

dequeuing any pending I/O interruption when the first general register indicates a second type response is to be provided, saving the state of a pass-through field in the interrupting subchannel, storing an I/O interrupt code for the pending interrupt at the address in the second general register, and setting a condition code in the host PSW to a third value to indicate the second type response has been provided.

21. A method of restricting guest operations in a data processing system as defined in claim 8, further comprising:

a dispatched guest generating an intercept code and putting it into the guest'"'"'s SD to indicate the guest cannot process its I/O interruption because conditions exist preventing the guest from currently handling the interrupt,

intercepting the guest processing by passing control of the CPU to the host in response to the guest indicating an intercept code, and the host processing including;

testing a pass-through field in the interrupting subchannel to find if it is in a state allowing partition-assigned guests to handle the subchannel'"'"'s interruptions,

moving the pending I/O interruption from the hardware queue to a guest queue assigned in the subchannel to receive interruptions of the subchannel for the guest,

setting on the dispatched guest'"'"'s SD disabling field to indicate the guest is currently disabled from handling a pending I/O interruption for a subchannel assigned to the guest and being stored in a guest'"'"'s I/O interruption queue while the guest is disabled,

the host passing control of the CPU back to the guest to continue guest processing when the pass-through field is set to a state allowing partition-assigned guest'"'"'s to handle the interruptions of the subchannel.

22. A method of restricting guest operations in a data processing system as defined in claim 8, host processing for a diagnose compare and swap instruction (DCSI) for setting a pass-through field in a subchannel, further comprising:

finding that no exception conditions exist at the beginning of execution of the DCSI that may interfere with its execution to continue the execution of the DCSI,

setting on a lock field in the subchannel,

testing if the pass-through field in a third operand is set on, and if set on testing if the subchannel is on an I/O interruption queue, and dequeuing the subchannel if found on a queue,

comparing the status pending field and the pass-through field in the first operand with corresponding status pending and pass-through fields in the subchannel,

setting the pass-through field in the subchannel to the new value contained in the third operand of the DCSI if equality is found by the comparing operation,

but when inequality is found by the comparing operation, setting the first operand from the current status pending and pass-through fields in the subchannel,

generating a condition code in a program status word (PSW) of a guest for which the DCSI is being executed by setting the condition code to a first value when equality is found, and setting the condition code to a second value when inequality is found, and

setting off the lock field after the condition code is generated.

23. A method of restricting guest operations in a data processing system as defined in claim 1, chanel address relocation for channel accesses in an assigned zone in MS, further comprising:

providing in each subchannel any AZN assigned to the subchannel and the upper and lower limit MS addresses assigned to the AZN,

adding the lower limit address to each channel address to be accessed in MS to obtain a resulting relocation address, and

comparing the reslting relocation address to the upper limit address,

suppressing the MS access by the resulting relocation address if it is greater than the upper limit address.

24. A method of restricting guest operations in a data processing system as defined in claim 1, CPU address relocation for CPU accesses in assigned zones in MS which can have different sizes, the assignment of MS to a partition comprising:

generating a host segment table and a plurality of guest segment tables, a segment table being provided for each operational guest in the data processing system and a host segment table being provided for the host,

setting a guest control register to an MS address of the guest'"'"'s segment table, and setting a host control register to an MS address of the host segment table,

allocating a contiguous set of page frames in MS between the upper and lower limit MS addresses assigned to the respective AZN of each guest,

generating at least one host page table for each guest, the host page table(s) for the guest containing a contiguous set of entries corresponding to the page frames allocated to the respective guest,

setting the page table entries in a guest'"'"'s page table(s) to the respective absolute addresses of the page frames in MS allocated to the guest, and setting to a valid state each of the guest'"'"'s page frame entries,

also setting a segment table entry in the host'"'"'s segment table to the absolute address of each host page table for the guest in MS while maintaining the order of segment table entries for the guest in the host segment table consistent with the order of contiguous page frames in the guest'"'"'s page tables if there is more than one host segment table entry for the guest,

on the dispatch of a guest, loading the host segment table address into the host control register in the CPU and loading the guest segment table address from the guest'"'"'s SD into a guest control register in a CPU on which the guest is being dispatched,

performing address translations for the guest absolute addresses using the host segment table entry(s) and page table(s) for the guest accessed through the host control register in the CPU.

25. A method of restricting guest operations in a data processing system as defined in claim 24, address relocation for a page in an assigned zone in expanded storage (ES) comprising:

adding a guest-provided page number to be access in ES to the lower limit page number obtained from the partition definition set for the respective guest to obtain a resulting relocation page number,

comparing the resulting relocation page number to the upper limit page number obtained from the partition definition set,

suppressing the ES access by the resulting relocation page number if it is greater than the upper limit page number.

26. A method of restricting guest operations in a data processing system as defined in claim 1, enabling the sharing of an I/O device and its control unit between a plurality of partitions, further comprising:

having an I/O processor connected to a plurality of I/O subchannels and a plurality of I/O channels, in which the plurality of subchannels need not be equal to the plurality of channels, each channel being capable of controlling a transmission of a stream of data between channel-program designated addresses in MS and the I/O device and its control unit, and each subchannel being capable of controlling the operation of an I/O device, each channel also being capable of providing a separate transmission path between associated I/O devices and MS,

connecting one side of an N-way switch to the control unit for the I/O device, and connecting another side of the N-way switch to N number of I/O channels for providing N-way switching of the device and its control unit to any selected one of the N number of channels, the device switch operating under manual or program control to connect the I/O device and its control unit to any channel connected to the device switch,

providing up to C number of copies of a subchannel that controls the operation of the I/O device, in which all C number of the subchannel copies designate the same I/O device,

selecting C number of different partitions, and assigning each of the C copies of the subchannel to a different one of the partitions, the selected partitions respectively having C number of different zones in MS, and

further assigning each of the C number of subchannel copies to one or more of the N number of channels connected to the device switch to enable the device switch to operate under manual or program control to connect the I/O device to any of the C number of different zones in MS through a device switch selected channel in order to allow data transmission between the I/O device and any one of the C number of zones as selected by the device switch under manual or program control.

27. A method of restricting guest operations in a data processing system to system resources assigned to a guest, the system resources in the system including one or more real CPUs, a system main storage (MS), an optional system extended storage (ES), and a plurality of I/O channels usng I/O processors for connecting to the system a plurality of I/O device control units with their I/O devices, a host hypervisor (host) which includes software, the host supervising plural software control programs (guests) capable of concurrently and independently operating in the system and the guests may be the same or different types of control programs, subchannels (SCHs) for representing I/O devices to the host and to the guests, each guest being restricted to using an assigned subset (partition) of system resources, the method for restricting guest operations comprising:

providing a plurality of partition sets in system storage for defining partitions of system resources, each partition set defining a particular subset of system resources available to a guest assigned to use the partition, each partition set comprised of a plurality of items for specifying the system resources assigned to the partition and the items being enterable by a human operator, the items assignable to each partition set including indicators for;

a partition identifier unique to each partition set, a MS zone of contiguous main storage which can be located anywhere in MS and bounded by upper and lower limit MS addresses, none or one or plural SCHs, and an optional ES zone located anywhere in ES and bounded by upper and lower limit ES addresses,

having a control block in system storage for each SCH, each SCH having an identifier for an I/O interruption queue assigned to the SCH, each SCH being capable of being associated with none, one or plural partition sets,

also having a plurality of state description control blocks (SDs) in system storage for representing logical CPUs in the system, each SD containing fields with parameters for defining a logical CPU,

binding a logical CPU to a particular partition by associating a respective partition set with the SD representing the logical CPU,

assigning a logical CPU to a particular guest by entering parameters of the guest into the SD of the logical CPU,

dispatching a logical CPU for a guest on a selected real CPU in the data processing system by the host executing a start interpretive execution (SIE) isntruction on the real CPU to start execution of the logical CPU for the guest,

assigning an I/O device to a guest by associating an SCH of the I/O device with the guest'"'"'s partition set and with the SD of a logical CPU which is to be used by the guest,

setting a pass-through indicator in the SCH of an I/O device assigned to a guest to enable the direct routing of I/O instructions from, and of pending I/O interruptions to, the logical CPU of the guest in order to allow each guest to directly control guest assigned I/O devices without host assistance during normal exeuction of I/O operations by a guest'"'"'s logical CPU,

allowing a guest to directly instruct, and to directly handle I/O interruptions for, an I/O device assigned to the guest by determining that the SCH of the I/O device is associated with the SD of the logical CPU dispatched for the guest to allow the guest to control its assigned I/O devices without host intervention, while restricting each guest to using only the SCHs and other system resources defined in the partition set assigned to the guest.